The traditional RDH method for JPEG bitstream is conducted by building the mapping between the variable length codes (VLC). However, the capacity is limited, and the file size may not be well preserved as the capacity is increased. This is because that the trade-off between the capacity and the file size has not been deeply investigated, neither explicitly formulated nor appropriately optimized. In this paper, we propose to take the file size preservation into consideration and minimize the file size increase for a given capacity. We use the value transfer matrix to simulate a theoretical model and then design some optimization rules to reach the reversible solution. Consequently, a better reversible VLC mapping can be obtained in terms of both the capacity and the file size preservation. The experimental results show that the proposed method can increase the capacity with a relatively low cost of file size increase.

JPEG比特流的传统RDH方法是通过在可变长度代码（VLC）之间建立映射来进行的。但是，容量有限，并且随着容量的增加，文件大小可能无法很好地保留。这是因为尚未深入研究容量和文件大小之间的折衷，既未明确制定公式，也未进行适当优化。在本文中，我们建议考虑保留文件大小，并在给定容量的情况下最小化文件大小的增加。我们使用值传递矩阵来模拟理论模型，然后设计一些优化规则以达到可逆的解决方案。因此，就容量和文件大小保存而言，可以获得更好的可逆VLC映射。